The present invention is directed to a device for electro-optically measuring the voltage in a high voltage conductor, whose electrical field will elliptically polarize either a linearly polarized light beam or a circularly polarized light beam in a light conductor or guide and the device includes a receiver which will measure the voltage in response to the phase differences of the light beam components with different transit speeds in the light wave guide.
The dependency of the birefringence upon an external electric field is commonly disignated as an electro-optical effect. Upon transit through a birefringent medium, a linearly or a circularly polarized light beam is generally elliptically polarized. The components of the light wave or beam, which components are associated with the two main axes of the birefringent medium, will move through the medium with different speeds. The resulting phase difference is proportional to the distance traveled by the light beam in the crystal or medium and if the material has a linear electro-optical effect and the birefringence disappears when the field is not present, the amount of the phase difference is proportional to the electrical field. Thus, the phase difference can be utilized for measuring the field strength and for also measuring the voltage creating the field.
Methods for voltage measurements are known wherein the electrical field itensity E is determined with the electro-optical effect in unsymmetrical crystals or with the aid of a field influence on liquid crystals. However, only the electrical field intensity in the comparitive small crystal volume is thus determined.